Add examples of Logger-based logging to demo.py

demo.py

@@ -1,7 +1,11 @@
 #!/usr/bin/env python
+import time
 
 import easy_tf_log
 
+# Logging using the global logger
+
+# Will log to automatically-created 'logs' directory
 for i in range(10):
     easy_tf_log.tflog('foo', i)
 for j in range(10, 20):
@@ -13,3 +17,18 @@
     easy_tf_log.tflog('baz', k)
 for l in range(5):
     easy_tf_log.tflog('qux', l, step=(10 * l))
+
+# Logging using a Logger object
+
+logger = easy_tf_log.Logger(log_dir='logs3')
+
+for i in range(10):
+    logger.log_key_value('quux', i)
+
+logger.log_list_stats('quuz', [1, 2, 3, 4, 5])
+
+logger.measure_rate('corge', 10)
+time.sleep(1)
+logger.measure_rate('corge', 20)  # Logged rate: (20 - 10) / 1
+time.sleep(2)
+logger.measure_rate('corge', 30)  # Logged rate: (30 - 20) / 2